I have a client using SBS2003 with exchange 2003. They are not able to receive email from some domains. We are using Mcafee Groupshield 6.0 with the anti-spam add-on. I have recruited a user at one of the domains that we are having issue with to help me to troubleshoot this and send test messages to my client and copy me, I receive all of the messages they send.
I have turned ALL SMTP logging on that I know exists. NONE of the logs show an attempt to connect from any of the domains we are having issue with to my clients server, but my messages do appear in the SMTP logs. My client can send messages to them with no problems. I have checked the anti-spam logs and nothing is logged. My client, and the domains in question are not listed in any of the blacklists (147 of them) located in the blacklist search at MX Toolbox.
I am at a loss here. If it was one domain I would say it was on their end, but, it appears to be several domains that we are having the issue with. So, That leads me to believe it is on our end.
Any help is greatly appreciated.
My client and I are use the same ISP, and Our servers are setup nearly Identically.